Insect repellent containing aliphatic alcohols



Patented Sept. 2, 1941 INSECT REPEILEN'I CONTAINING ALIPHATIC ALCOHOLS Anderson W. Ralston and John P. Barrett, Chicago, Ill., assignors to Armour and Company,

Chicago, 111., a corporation of Illinois No Drawing. Application September 5, 1939, Serial No. 293,522

Claims.

This invention relates to repellents for insects such as mosquitoes, flies, and gnats and more specifically to repellents comprising aliphatic alcohols containing from ten to fourteen carbon atoms.

Both humans and animals are annoyedby insects and this problem is so acute as to render certain regions. essentially uninhabitable by man. Disregarding the annoyance, insect bites are often accompanied by profound and in some cases serious physiological efiects. Many. diseases, particularly those of tropical origin, are transmitted by means of insect bites. In spite of man's constant warfare against insects they still occur in large numbers and they continue to plague both man and animals. Insecticide chemists have devoted considerable time and effort to this problem. Thousands of compounds have been tested for their toxic effect upon insects. These compounds either act as stomach poisons or respiratory paralyzers and are effective in a number of instances.

Another approach to the problem, which has also been given considerable thought, is the development of substances which have a repellent eifect upon the insects. applied upon the host in a variety of manners and serves to prevent attacks by insects which under normal conditions are attracted to these individuals.

Toxicity and repellency are not usually correlated, and it does not follow that a substance toxic to the insect is in any way-repellentto it. On the other hand materials that are repellent to insects are not generally toxic and in a number of cases effective repellents are actually harmless to insects.

In order to be effective for this purpose the substance must, of course, possess a high degree of repellency. In addition they must not be toxic or harmful to the individual treated. In general, it is believed that repellents are irritating to the sensory mechanism of the insect. It does not follow that a substance possessing this sensory irritating efiect upon insects has a similar effect upon humans or animals. In a number of instances substances which definitely repel insects are pleasing to man and substances repugnant to man are attractive to insects.

' We have experimented extensively with various materials which might have insect repellent properties, and have now discovered that aliphatic alcohols having ten to fourteen carbon atoms are extremely effective insect repellents.

Before describing ways-by which our discov- These substances can be.

eries can be put to practical use we shall first show the efiectiveness of our alcohols in comparison with other materials and in comparison with alcohols of less or greater carbon atom content. The testing method with' flies is as follows: Three to four hundred adult domestic flies (Musca domestica) are confined in a sixteen mesh screened cage. The inside dimensions of the cage are: height, 19.5 inches; width, 9.5 inches, and length, 14.5 inches. The top and bottom, and also the two narrow sides, are of wood and the two broad sides are covered with sixteen mesh screening. The cage is equipped with a trap door for the introduction of water, food, and test samples. The flies used are of known age and are grown under laboratory conditions. Six hours prior to each test the food is removed from the cage. Water is present at all times. The tests are conducted at a constant temperature of 85 F. and 65% relative humidity. Two grams of malt extract (Dimalt extract Fleischmann) are placed in the middle of a seven centimeter filter paper and spread into a circle approximately two inches in diameter.-

These are then placed for a period of from ten to twelve hours in a constant temperature oven v (37 0.). The purpose of this baking is to dry the extract so that it will not flow from the test piece. One drop of the compound to be tested is then placed in themiddle of the malt extract.

disk, and spread uniformly over the surface of the malt. These are introduced into the cage after a period of fifteen minutes. The disks are pinned to the inside screened surface of the cage. They are placed in the cage in such a manner that the untreated surface of the disk faces the light. Generally four or five disks are placed in each cage and in every case one of the disks contains only the malt extract. This serves as a check and all results are referred to it.

The principle of this procedure is to protect a known attractant. The malt is attractive to the flies for whom it is served as food. The natural tendency of the flies, therefore, is to be attracted to. and eat the malt. The repellent properties of the test compound are measured by its ability to overcome this natural, tendency. The order of repellency of compounds is easily tested by this method since the fiieswill eat all of the malt upon the most attractive disk and after exhaustion of this malt will go to the test sample least repellent. In the case of highly repellent compounds no flies will eat the treated malt or light upon the disk containing it.

Fifteen minutes after the introduction of the test sample the number of flies feeding upon each disk is recorded. Counts are made at half-hour intervals thereafter for a period of at least three hours.

As stated, primary alcohols containing ten to fourteen inwe have discovered that aliphatic 5 Table 4 shows the repellent action of decyl, undecyl, and undecenyl alcohols.

TABLE 4 Repellent action of decyl, undecyl, and andecenyl alcohols (number of flies) elusive carbon atoms are excellent insectrepellents and that these alcohols can .be used Alcohol either by themselves or admixed with other sub- Time in'mmutes stances. The following tables compare these Check D 1 U d 1 U d 1 alcohols with other substances. (mmam m n m n may TABLE 1 e1 3 1 o Repellent action of lauric acid and dodeayl it t g g alcohol (number of flies) g p g 22 1 o 1 Compound 188 I 7 z a Timeinmmm The results tabulated in Table 4 Show decyl Ch 1: n a 1 1. i (Dir alt) oioofi 3:13 undecyl, and undecenyl alcohols to be quite highly repellent. These alcohols containing ten 19 o 14 and eleven carbon atoms, the undecenyl alcohol $8 2, g being unsaturated.

1s 0 9 Table 5 shows the repellent action of tridecyl {g 8 1 alcohol and tetradecyl alcohol. 106 1 35 Tests 5 The results shown in Table 1 show lauric acid Repellent actilm tfidecill n t r will to be only mildly repellent and dodecyl alcohol to alcohols n r of fl be highly repellent.

Table 2 shows the repellent action of various Alcohol fatty acid derivatives compared with onus; Time, minutes citronella. Oil of citronella was chosen for heck 1 comparison because or its known repellent action. 1 (131mm,) mam! Temdecy TABLE 2 a2 1 o Repellent action of lauric acid, stearonitrile, oil 3 3 of citronella and dodecyl alcohol (number of 8 flies) 11 1 o 164 4 4 (31 11250 :351 i i z l clt l l la 21%?5 The results recorded in Table 5 show tridecyl and tetradecyl alcohols to be quite highly rec1 53 as o 1 pellent. But when the number of carbon atoms 22, 3 g g 3 increases to sixteen (hexadecyl, Table 3) re- 36 10 10 a 1 pellent action decreases rapidly.

2, g g 2 3 Table 6 shows that the alcohols we use can 15 4 12 a 0 i be perfumed without decreasing the repellent 1a 4 a 4 0 223 105 185 10 2 Wwer- Team: 6

, These results show that lauric acid and stearonitrile are inferior to oil oreitronella as an insect Repellent action of perfumed and unperfumecl dodecul alcohol (number of flies) repellent and that dodecyl alcohol is superior to oil of citronella. Sample Table 3 shows the repellent action of several Tim in in w alcohols. e m Perfumed o TABLE 3 (Di t) 35% l g fi Repellent action of octyl alcohol, dodecyl alcohol,

and hexadecyl alcohol (number of flies) 4a 1 0 4a 0 1 76 21 0 2 Alcohol 3 3 Time in minutes g g 8: 35 Qctyl Dodecyl Hexadwyl 63 27 9 48 65 The results tabulated in Table 6 show that the 39 207 l 54 perfumed dodecyl alcohol is the equivalent of 17 12 o 3 the unpertumed dorlecyl alcohol in repellent acii 2 3 '2 tion- I r 151 7a 9 16 The above results show that aliphatic alcohols containing rrom ten to fourteen carbon atoms The data presented in this table shows that hexadecyl alcohol is essentially without repellent action, octyl alcohol containing eight carbon atoms, is only mildly repellent, and dodecyl alcohol is strongly repellent. V

insects in question.

cage through the sleeves. If the compound possesses high repellent action the mosquitoes do not attack the operators ar'm. However, if the compound is mildly repellent or possesses no repellent activity they immediately attack the operator. These tests were performed using oil of citronella, stearonitrile, lauric acid, and the various alcohols described herein. The results show conclusively that alcohols from ten to fourteen carbon atoms inclusive possess a high degree of repellency for mosquitoes.

The aliphatic straight chain saturated and unsaturated alcohols haw'ng ten to fourteen carbon atoms also act as a repellent for ant and moths. For example, dusting powders consist-.

ing of an inert material, such as pumice, admixed with small amounts of the alcohols efiectively prevents the ingress of ants. Woolen materials containing traces of our alcohols are no longer attractive to moths.

Feeding tests of our alcohols using rabbits, rats, and guinea pigs showed the alcohols to be without toxic action. Dodecyl alcohol was injected subcutaneously without serious effect. Dodecyl alcohol rubbed upon the skin of humans, dogs, and rats was without effect.

Our discovery of the marked repellent action of the alcohols of our invention can be put to practical use in many different ways. Since the alcohols are without efiect on the human skin,

they can be lightly rubbed on the skin in much the same way as oil of citronella and thus efiectively repel the more common insects, such as flies and mosquitoes. Or the alcohols can be dissolved or emulsified in any suitable vehicle to give liquid products readily applied to the human skin. Paper can be impregnated with such solutions to give a paper product which, in sheet form, can be laid over exposed article of food in the kitchen and in the shop to preventflies from lighting thereon. Animal sprays likewise consisting of aqueous emulsions of the alcohols or solutions thereof in any suitable solvent, can be prepared and cattle sprayed therewith.

Since the gist of our invention is in the dis-- covery of the unusual insect repellent proper-.

ties of these aliphatic alcohols we claim our invention broadly in the appended claims. It will be readily apparent to those skilled in the art that our invention can be put to use in many different ways in accordance with prior applications of insect repellent materials.

Having thus described our invention, what we claim is:

1. An insect repellent having as its essential active ingredient a primary aliphatic alcohol having from ten to fourteen carbon atoms.

2. An insect repellent having as its essential active ingredient a primary aliphatic alcohol having ten to fourteen carbon atoms, together with aperfuming agent;

3. An insect repellent having as its essential active ingredient a primary unsaturated aliphatic alcohol having ten to fourteen carbon atoms.

4. An insect repellent containing decyl alcohol as its essential active ingredient.

5. An insect repellent containing dodecyl alcohol as its essential active ingredient.

ANDERSON W. RALSTON'. JOHN P. BARRETT. 

